1. Field of the Invention
The present invention concerns cam mechanisms of the positive type which in the textile industry are intended to ensure control of the heddle frames of the weaving looms. More particularly, the invention relates to the levers having double rollers with which the mechanisms of this type are provided.
2. History of the Related Art
In order to clearly set forth the problems associated with the roller assemblies which are currently used with conventional cam mechanisms for controlling the heddle frames of weaving looms, FIGS. 1-3 of the accompanying drawings disclose existing roller assemblies with FIG. 4 showing graphically some of the problems that relate to increasing the spacing between the cam members in order to provide clearance for some types of prior art roller assemblies. FIG. 1 of the accompanying drawings schematically shows the connection between the heddle frame of a weaving loom to one of a series of actuating levers. The number of actuating levers is generally equal to the number of frames. Further, each lever is provided with two follower rollers. The rollers are offset with respect to each other in order to cooperate with two tracks of a complimentry cam.
It should be understood, that if it is desired to give the frames an ample vertical displacement without the need to provide additional mechanical connections between each of the levers associated with each of the corresponding frames, it is necessary that the two conjugate tracks of each cam present profiles widely offset with respect to each other. Consequently, the levers and rollers must penetrate deeply between the two adjacent cams or else the lift of the cams or the stroke of the roller assemblies will be limited and result in increased stress on the roller assemblies thereby creating a shorter life expectancy of the whole mechanism by developing a premature fatigue of the component parts thereof.
Furthermore, it will be noted that the clearance that necessarily established between each of the roller assemblies and cam tracks is passed to the frames and is amplified by an amount equal to the ratio of the stroke of each frame to the stroke of the corresponding roller assemblies. This clearance at the frame is extremely detrimental at high speed as vibrations may be induced which would limit the effective life of the heddles and will thereby reduce the yield of the weaving loom.